Implement aggregation guidelines

sure , thanks

I will review today and perhaps we can compare notes tomorrow when I get into work?

i have created a pull request with the mod-users-bl rewrite. All endpoints have been implemented. this includes the /users endpoint which uses the rmb join functionality to return a list of composite users - with each composite user containing perms / creds / groups associated with the user. this incorporates the 'includes' trait.
- can you review?
i have not completed the testing - started looking into mocking via raml briefly, but am currently just rewriting marcs fakes

As discussed on the call: it would be good to include unit test for the new aggregation functionality. They may require mock/fake services, and Marc has examples of such services in mod-inv/mod-circ.